Relativistic Accretion into a Reissner-Nordstr\"om Black Hole Revisited

TL;DR

This paper investigates how relativistic and non-relativistic fluids accrete onto Reissner-Nordstr"om black holes, revealing differences in flow behavior and accretion rates compared to uncharged black holes, especially for relativistic fluids.

Contribution

It provides a detailed analysis of accretion dynamics onto charged black holes, highlighting how charge influences critical points, flow velocities, and accretion rates for different fluid regimes.

Findings

Relativistic fluids cross the critical point subsonically near the event horizon.

Accretion rate for relativistic fluids is about 60% less in extremal Reissner-Nordstr"om black holes.

Non-relativistic fluids show minimal change in critical point and flow velocity compared to Schwarzschild black holes.

Abstract

The accretion of relativistic and non-relativistic fluids into a Reissner-Nordstr\"om black hole is revisited. The position of the critical point, the flow velocity at this point and the accretion rate are only slightly affected with respect to the Schwarzschild case when the fluid is non-relativistic. On the contrary, relativistic fluids cross the critical point always subsonically. In this case, the sonic point is located near the event horizon, which is crossed by the fluid with a velocity less than the light speed. The accretion rate of relativistic fluids by a Reissner-Nordstr\"om black hole is reduced with respect to those estimated for uncharged black holes, being about 60% less for the extreme case (charge-to-mass ratio equal to one).